Best approach is probably a Gnome Warlord with a Trisword, but since they buffed this dungeon it's been a shoe-in for most difficult level in the game short of VGT. There really aren't a lot of great options here.

My two purist victories were Goblin Assassin (worship Tikki Tooki, Swift Hands everything that isn't level 10, fireball or PISORF everything else, work in melee attacks when possible) and Orc Rogue (worship Glowing Guardian, absolve everything that's level 1-2 and slaughter everything else), so with the appropriate preps those are both likely to be very successful strategies. (Granted, they're basically the two best all-around strategies in the game, IMO, so that's to be expected.)

I just want to brag briefly that I just completed my first Vicious run! Nothing too glorious--a Human Berserker in Dragon Isles--but I'm proud. GETINDARE is a really nice spell; it helped me defeat +2 level monsters that would have otherwise required a potion. I didn't prepare an altar, but found Dracul, which worked well for providing adequate health resources.

Hey guys, I've unlocked Vampire and Half-dragon, just gorgon left now O.o and ..... I find Naga City to be the hardest .... I actually found VHoS easier, so far I've tried: Human Bloodmage(Almost got it, think I made a mistake somewhere), Dwarven bloodmage and vampire (not played him much, but i got up 9 lifesteal ... really hard to level up with him tho, had to use a yendor midway from lvl 6 to 8), I can probably win with Orc Rogue, less certain about Paladin, so I need at least 1-2 more ways to win. How viable is Trisword as a prep? It's damn expensive, I've never actually prepped it ... the cost per boost is ... prodigious. Suggestions?

Paladin of Glowing Guardian and Orc Rogue of Glowing Guardian (use the GG prep) are two easy wins. If you want to bust out your trisword, prep Mystera and take a gnomish Warlord. Actually, you may not even need to prep Mystera since you'll get a pile of piety as an on-worship effect.